205309813 has 4 divisors (see below), whose sum is σ = 207126828. Its totient is φ = 203492800.

The previous prime is 205309789. The next prime is 205309817. The reversal of 205309813 is 318903502.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 318903502 = 2 ⋅159451751.

It can be written as a sum of positive squares in 2 ways, for example, as 59938564 + 145371249 = 7742^2 + 12057^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-205309813 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205309817) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 908338 + ... + 908563.

It is an arithmetic number, because the mean of its divisors is an integer number (51781707).

Almost surely, 2^205309813 is an apocalyptic number.

It is an amenable number.

205309813 is a deficient number, since it is larger than the sum of its proper divisors (1817015).

205309813 is a wasteful number, since it uses less digits than its factorization.

205309813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1817014.

The product of its (nonzero) digits is 6480, while the sum is 31.

The square root of 205309813 is about 14328.6361179283. The cubic root of 205309813 is about 589.9337405242.

The spelling of 205309813 in words is "two hundred five million, three hundred nine thousand, eight hundred thirteen".